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Buck regulator with LDO controller suits automotive apps

Posted: 05 Dec 2008 ?? ?Print Version ?Bookmark and Share

Keywords:buck boost regulator? LDO controller? automotive application?

Linear Technology Corp. has released the LT3570, a 36V, 1.5A(ISW) buck and boost regulator combined with a linear controller packaged in a 4mm x 4mm QFN or TSSOP-20E.

The LT3570 operates from a VIN range of 2.5V to 36V (40VMAX), making it suitable for the load dump and cold-crank conditions commonly found in automotive applications. Independent input pins can be tied together to run from a single input or can be run from independent input rails. The buck regulator can deliver up to 1A of continuous output current at voltages as low as 0.8V whereas the boost converter can deliver output voltages as high as 38V

The LDO controller combined with an external NPN transistor can be run from the output of the buck regulator for maximum efficiency or via an independent input pin for design flexibility, either way providing low noise operation. Switching frequency is user programmable from 500kHz to 2MHz, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands and is synchronizable from 650kHz to 2.5MHz. The combination of its 4mm x 4mm QFN package (or thermally enhanced TSSOP-20) and high switching frequency, which keeps external capacitors and the inductor small, provides a very compact, thermally efficient footprint.

Both the LT3570's buck and boost switchers utilize high efficiency 1.5A, 240mVCESAT switches, with the necessary oscillator, control, logic circuitry and LDO controller integrated into a single die. Special design techniques enable efficiencies of up to 88 percent over a wide input voltage range while current mode topology enables fast transient response and excellent loop stability. Other features include independent soft-start capability for each channel and thermal shutdown.

Pricing for the LT3570EUF starts at $2.95 each for 1,000-piece quantities. The LT3570EFE is packaged in a thermally enhanced TSSOP-20 and pricing starts at $3.05 each, for 1,000-piece quantities. The LT3570IUF and LT3570IFE are tested and guaranteed to operate from a -40C to 125C operating junction temperature and are priced at $3.39 each and $3.51each, respectively for 1,000-piece quantities. All versions are available from stock.

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